US2552895A - Vacuum gauge - Google Patents

Description

y 15, 1951 G. A. KUIPERS 2,552,895

VACUUM GAUGE Filed July 22, 1949 v 2 Sheets-Sheet 1 INVENTOR. I EORGE A. KU/PERS wpm A ran/vs rs y 5, 1951 s. A. KUIPERS 2,552,895

VACUUM GAUGE Filed July 22,1949 2 Sheets-Shea; 2

//f\ Z4 I INVEN TOR. GEORGE A. KU/PERS A 7' TORNE Y5 patented May 15, 1951 VACUUM GAUGE George A. Kuipers, Oak Ridge, Tenn., assignor, by

mesne assignments, to Eastman Kodak Company, Rochester, N. a corporation of New Jersey Application July 22, 1949, Serial No. 106,275

7 Claims.

This invention relates to vacuum measuring devices and is particularly concerned with mechanical means for measuring reduced pressures.

The widespread use of vacuum equipment has created a need for accurate measuring devices for determining the degree of vacuum. Gauges employed heretofore have been generally of two types. The first type provides an indirect method by measuring some physical property of the gases in the evacuated system as in the case of the ionization gauges and thermocouples. The second type of gauge is a manometric gauge wherein a volume of gas from the evacuated system is compressed and the original pressure of the gas is determined manometrically by means of the gas laws.

It is an object of this invention to provide mechanical means for measuring reduced pressure.

It is a further object of the invention to provide vacuum measuring apparatus free of sensitive elements subject to contamination.

It is another object of the invention to provide simple and compact vacuum measuring apparatus.

Another object of the invention is to provide vacuum measuring devices adaptable for use over a wide pressure range.

Another object of the invention is to .provide means for accurately measuring vacuum in the range below 1 micron pressure.

Other objects will be apparent from the drawings, description and claims.

These and other objects are attained by means of this invention which is best illustrated with reference to the accompanying drawings.

Of the drawings:

Fig. 1 is a perspective view partly broken away and in section illustrating the internal mechanism of a simple gauge embodying the invention;

Fig. 2 is a perspective View partly broken away and in section of a preferred modification of the gauge shown in Fig. 1; and

Fig. 3 is a schematic representation of preferred driving means for the gauges of Figs. 1 and 2.

An illustrative embodiment of the present gauge as shown in Fig. 1 comprises tubular side wall I and disc-like end walls II and [2 which together define a gas-tight vacuum chamber.

Extending into the chamber in the region of the radial axis of the chamber is rotatable drive shaft l3 which enters the chamber through a packed gland opening (not shown) in end wall [2, the extension of shaft l3 outside the cham- 2 ber being coupled to the driving mechanism shown in Fig. .3.

Conduit l4 communicates with the chamber through aperture I6 in ide wall II], the conduit being adapted to be connected to an evacuated system on which pressure measurements are to be taken.

Rectangular driving vane ll is mounted on shaft l3 so as to oscillate when shaft I3 is actuated by the driving mechanism.

Vane ll, which is preferably constructed of a thin sheet of metal such as aluminum or the like extends outwardly from shaft l3 to a point contiguous to but out of frictional contact with side wall Ill. The lateral edges of vane l! in like manner are contiguous to but out of frictional contact with end walls II and [2. In gauges adapted primarily for measuring very low pressures, the spacing between the vane edges and the walls should be such as to minimize fluid flow between them in order to obtain sufficient pulsing pressure on the indicating vane to give a readily measurable oscillation with a relatively small amplitude oscillation of the driving vane.

Indicating vane 18 is pendulously mounted in the chamber by means of jewel supports (not shown) supporting upper edge 2!] of vane l8. Vane I8 is free to swing in pendulum-like fashion about upper edge 20 as an axis of oscillation. Like driving vane H, the edges of vane I8 are contiguous to but out of frictional contact with walls I0, II and I2.

Shaft 13 may be oscillated to oscillate vane I! by any suitable driving mechanism as, for example, the mechanism schematically illustrated in Fig. 3 in which shaft I3 is coupled to pinion gear 2| which in turn engages rack 22 mounted on movable shaft 23. Movable shaft 23 is coupled to reciprocating member 25 by means of connector 26 and pivots 21 and 28. Connector 26 swivels on fulcrum pin 29 which is adjustable along connector 26 in order to permit controlled variation of the relative motion of shaft 23 and reciprocating member 25. Member 25 is pivotally secured to driving arm 24 which is mounted for rotation around one end of arm 24, arm 24 being rotated by suitable actuating means (not shown).

In operating the gauge of Fig. 1, conduit I4 is connected to the evacuated system on which pressure measurements are to be made. After lapse of time sufficient for the gauge chamber to be evacuated to a pressure corresponding to the system being measured, the driving mechanism of Fig. 3 is actuated and shaft I3 is thereby ropulsing pressure on vane I8 and it begins to iswing in pendulum-like fashion in a direction normal to the plane of vane it until its frequency reaches the constant frequency of oscillation of driving vane l'l. I

At that point, the pulsing pr serves merely to maintain the angle of oscillation of vane [3 at the maximum,amplitude cgnn mensurate with the pulsing pressure being transmitted from vane ll and so long as vane la'maintains the maximum amplitude of oscillation, the compression-of gases in the chamber is negligible and the pulsing force of driving van'ei'i isdirectly' tr'ansmitted to indicating vane -I8.-- Ehus by means of continued pulsing pressure, indicating vane 1-8- is caused to-oscillate at an amplitude muchgreater than would'r'esult from a single oscillation of driving vane ll whereby the gauge is operable at very low pressures.

The angular displacement of indicating vane at its maximum value is thereupon measured by any suitable -r'neans. -For example, the end wall I l'can-be constructe'd of transparent material with angular'scales l5 and I9 superimposed on the facethere'ofto provide a direct reading of the amplitudeofoscillation of each vane.

Alternatively, the; gauge can be operated to cause indicating vane [8 to oscillate through a predetermined fixed angle as,--for example, 4, and the amplitude of oscillation of vane ll 7 necessary to oscillatevane [8 through 4 can be measured either directly on angular scale H3 or by'calculation,fromfthe observed linear stroke of movable shaft" 2 3f ofthe drivingmechanism.

, f'rneg'augeembcdying this invention isadapt'ed for use overa wide pressure range. lt' 'isof 'pars r fi tv in s g. W 110W P ur where conventional gaugesisuifer "greatest losses .inse si iyi n a r r s e w ne .i ni b a for... am le at e su wini e. re i n 0f ,l -imms. h fivin vane slc i di q q sil a at the natural frequency of thependulum indicatingyanewhereby the pendulum indicating vane .will .oscillate ,at. its natural period. a At resonance frequency, the .pulsing pressure necessary to oscillate the indicating. vane isinfinitesimal andleakagenaround the edges of the vane isv not objectionable. ..The gauge is thus able to provide extremely sensitive measurement at pressures approaching zero.. At higher pressures,

it is not necessary to oscillate the driving vane at resonance frequency although such oscillating frequency is wholly satisfactory.

The period T of the indicating vane can be calculated from the equation for the pendulum-== at infinitesimal amplitude I=moment of inertia;

m=mass of vane; V

wherein g=acceleration ofgravity; and A h=distance of center of gravity from the axis.

4 Since for the vane length r,

l L 3 and the equation for period becomes:

Inconstructingthe gauge, therefore, a predetermined'priodmay be chosen, as for example '014Q's1ecohd, in which case the length of the vane is'cho sn accordingly; or the vane may be constructed and its period calculated.

when the'indicating vane is caused to oscillate through a predetermined angle, the amplitude ofoscillationof the driving vane being increased until the indicating vane reaches the desired "angular displacement, the angle of oscillation T0 of the driving vane is readily calculated from the'formula: l

, 77/1- 7 L W M -L w er in.-,-

. n1 =number 9f teeth per inch in rack 22 na -number of teth gamma 2' ql zlineianstroke of calm25 .t di n' ronstars to anagram M=length of connector 26 H p v A-preferred embodiment of. the invention,;as. shownin Fig. 2, comprises, as in Fig.1, a vacuum chamber defined, lay/walls 11.0,. i l. and .l 2, which chamber is provided with conduit l4. Drive shaft 13"supports Land actuates the 'drivingnzane as set out hereinabove; "but. in this. embodiment, driv-v ing vane Ila extends diametrically across the; chamber substantially as shown... Door-like.- member'fill marginally encloses, indicatingflvane; [8 which is supported pendulouslygatits upper edge, on .knife edges or jewel, supports, (not.

shown) A. small "shield *3] is fastened ;to vane I8 in vertical alignment with windows 32, in

end'wallsill andIZ,

In the :preferred method of :operating the gauge shown in Fig; 2,,i-indicating vane ity is. "caused to oscillatethrough-an angle of 4. The.

"amplitude of oscillation is'determined by having shield 3| and windows 32 soxspa'cedthat.

.when a beam 'of light; is directed through wimdows 32, the beam is completely'blockedmomen itarily'by shield 3 i'atthe furthest point of swing; "of vane l8'a't thede'sirfed angle of oscillation.

Drivinglvane Ila; is oscillated by shaft it; so as; to cause vane 18 to oscillate ;andthe-amplitude 10f oscillationof vane .l lanecessary; to drive vane 1L8 through'theidesiredfixed angle is readilymeasured as describedv hereinabove, M V "The equation of motion of the indicating vane is as follows: 7

angular displacement of vane 18 1 i tiine of swing f'm'massjof vane 13 -g=,acceleration of'gra'v'ity r =length of vane l8 I=moment of inertia ofvane l8 1 W g hg constant 1: i -pz)"' ,difference in pressures onppposite faces It has been found that the equation holds regardless of the leakage around the edges of the vanes, and at higher pressures it is often desirable to perforate the driving vane in order to reduce the amplitude of oscillation of the indicating vane. At low pressures, leakage should be minimized in order to facilitate reading of the gauge by maintaining'oscillation at a readily measurable value.

Thus, by means of this invention, vacuum is measured by direct mechanical means of simple construction. By the use of a pulsing driving force, compression effects are minimized. The gauge is useful over a wide range of pressures, and extremely low pressures are readily measured by pulsing the driving vane at the natural frequency of the indicating vane. f

While the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scop of the invention as shown in the drawings, described herein and as defined in the appended claims.

What I claim is:

1. A vacuum gauge comprising in combination wall means defining a gas-tight vacuum chamber, conduit means communicating with said chamber and adapted to be connected to an evacuated system, a plate-like driving vane, means for pivotally mounting said driving vane in said chamber, driving means for imparting periodic oscillatory motion to said driving vane in a direction normal to the plane of said vane, a plate-like indicating vane, means for pendulously mounting said indicating vane in free swinging movement about its upper edge in a direction normal to the plane of Said indicating vane, and means for measuring the amplitude of oscillation of said driving vane and said indicating vane, said vanes together with said wall means being arranged to partition said chamber into a confined zone between said vanes whereby oscillatory motion of said driving van periodically compresses gaseous fluid in said zone.

2. A vacuum gauge comprising in combination wall means defining a generally cylindrical vacuum chamber, conduit means communicating with said chamber and adapted to be connected to an evacuated system, a plate-like driving vane, means for pivotally mounting said driving vane in said chamber for oscillatory motion about the radial axis of said chamber in a direction normal to the plane of said vane, rotatable driving means associated with said driving vane and arranged to positively actuate said driving vane in periodic oscillatory manner, a plate-like indicating vane, means for pendulously mounting said indicating vane in said chamber for free swinging motion about the upper edge of said indicating vane in a direction normal to said upper edge, said indicating vane being mounted with the upper edge of said indicating vane parallel to said radial axis of said chamber, said vanes and said wall means being arranged to partition said chamber into at least two confined zones whereby oscillatory motion of said driving vane is transmitted to said indicating vane by pressure on gaseous fluid in said zones, and means for measuring the amplitude of oscillation of said driving vane and said indicating vane.

3. A vacuum gauge comprising in combination cylindrical side wall means and disc-like end wall means defining a cylindrical vacuum chamber, ,a rotatable driving shaft extending into said chamber along the radial axis of said chambed a rectangular driving vane mounted on said shaft with the plane of said vane parallel to said shaft,- sai'd driving vane'extending outwardly from said shaft and having the edges of said vane contigu ous to said cylindrical wall meansand-endwalt means, an indicating vane, means for pendulously mounting said indicating vane in said chamber in a plane parallel to said radial axis, saidindi=- cating vane being free to swing in pendulumlike fashion in a direction normal to the plane or said indicating vane, said indicating vane having the edges thereof contiguous to said end wall. means, said indicating vane extending substantially the extent of the radius of saidchamber' from said radial axis to said cylindrical wall means, whereby said chamber is partitioned into confined zones by said vanes, reciprocating driv mg means for actuating said driving shaft and imparting periodic oscillating motion to said drivmg vane, and means for measuring the amplitude of oscillation of said vanes.

4. A vacuum gauge comprising in combination a tubular side wall and disc-like end walls defining a cylindrical vacuum chambenconduit means communicating with said chamber and adapted to be connected with an evacuated system, a rotatable drive shaft extending into said chamber and lying along the radial axis of said chamber, a flattened rectangular driving vane having one end mounted along said drive shaft and extending outwardly from said shaft toward said tubular side wall, the lateral edges of said vane being contiguous to the end walls of said chamber and the free end of said vane being contiguous to said tubular side wall, driving means including rack and pinion means coupled with said shaft and arranged to oscillate said shaft and thereby oscillate said driving vane, a flattened rectangular indicating vane, means for pendulously mounting said indicating vane from its upper edge in said chamber for free swinging motion about said upper edge of said indicating vane, the upper edge of said indicating vane being parallel to said drive shaft, said indicating vane being spaced around the chamber from said driving vane, the lateral edges of said indicating vane being contiguous to said end walls of said chamber, said indicating vane extending from the region of the radial axis of said chamber substantially to said tubular side wall, and means for measuring the amplitude of oscillation of said indicating vane and said driving vane.

5. A vacuum gauge comprising in combination wall means defining a vacuum chamber, said wall means comprising tubular side wall means and disc-like end wall means closing the ends of said side Wall means, a rotatable drive shaft extending into said chamber along the radial axis of said chamber, a flattened rectangular driving vane mounted on said shaft in said chamber and extending diametrically across substantially the extent of said chamber, the edges of said driving vane being contiguous to said wall means around the marginal extent of said driving-vane, driving means coupled with said shaft and arranged to oscillate said shaft, a flattened rectangular indicating vane, means for pendulously mounting said indicating vane in said chamber along one edge of said indicating vane, said indicating vane being free to swing in pendulum-like manner with said edge being the axis of rotation, said indicating vane extending substantially across said chamber between said end wall means and extending from the region of said radial axis of said chamber outwar y sub an a nt said side wall mea sisaid indicating vanenormally bein in a plane Parallel said radial axis: of said chamber, and means for indicating; the amplitude of oscillation of, said driving; vane and said inating vane.

6. A. vac um gauge; cQmprising in combination wall: me ns definin a. va u m chamber and pa 6,: vane, means. partitioning said. chamber, sa all mea skand said vane means, combining to. define a generally confined zone between said aj-red vanemeans, said vane means having margins contiguous o; said, wall means but. out of in tienalcontact; with, said wall means, said R Qdiv neame nszcfizmp is gafla ened' drivin vane rigidlv-mennted ona rotatable shaft extendae nta said: cham erand a flattened, indicatin vane penduleuslvmeuntedgint said chamber alone one edge fsaidin icat n -vane and free. to swin in; nendulnmdike manner with said edge being the; axis: of; rotation, oscillatory driving means cqupled to; said rotatable; shaft and arranged to rotate said shaft in reciprocal fashion and therebyoscillate; said driving vane, and: means indicat ing; the amplitude of oscillation oif said driving vane and said indicating vane.

'1'. A; vacuum measuring devicecomprising in combination, within a closed chamber having communication with an evacuated zone, or an oscillatable driving vane adapted to create periodic; pulsations in the gas insaid chamber and a swingable; indicating vane movable. in pendulum fashion'in response to said pulsations. V

GEORGE A. KUIPERS.

REEERENCES CITED- UNITED STATES Name Date Langmuir Jan. 26, 1915 Number

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